Magnetic heads used in the production of magnetic media drives, e.g., magnetic tape and magnetic disk drives, are susceptible to error producing write relaxation induced Barkhausen ("popcorn") noise. Such popcorn noise is characterized by a single high frequency pulse generated internally by the magnetic head after the head has been written to. Although the occurrence of popcorn noise is difficult to predict, some magnetic heads exhibit a higher propensity for producing popcorn noise than others. Magnetic heads may be tested at the manufacturing stage to screen out those heads exhibiting an unacceptable popcorn noise characteristic.
The manufacturing and testing of magnet heads typically takes place in an industrial environment having a wide assortment of electrical equipment which produce electrical noise. A large part of this externally produced electrical noise is characterized by short bursts of high frequency pulses. These pulses are often detected by the magnetic head under test or by the testing equipment itself and interfere with the detection of true popcorn noise events, i.e., each burst of pulses may falsely counted as multiple popcorn noise events. Ultimately, the popcorn noise characterization of a magnetic head under test may depend more on the externally generated noise pulses than on the internally generated popcorn noise, leading to rejection of otherwise acceptable magnetic heads.